INTERCHANNEL-TIME CODING METHOD FOR MULTICHANNEL TRANSMISSION SYSTEMS

Abstract

A coding method for multichannel optical transmission systems (10) is described, in which coding is carried out both in the time direction and over a plurality of channels, a mapping being selected for the coding such that the simultaneous occurrence of bits with a signal value of ‘1’ in neighbouring channels is excluded. A multichannel optical transmission system for carrying out the method is furthermore described, as well as a coder (12) for use in conjunction with such a multichannel optical transmission system (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will be described below with reference to the accompanying drawings in which:

FIG. 1 shows a schematic representation of an optical transmission system with interchannel-time coding.

FIG. 2 shows a schematic representation of the channel patterns of multichannel transmission systems compared with one another,

FIG. 3 shows a diagram which plots the bit error rate (BER) of different multichannel transmission systems compared with one another, against the optical signal-to-noise ratio (OSNR), and

FIG. 4 shows a diagram which plots the bit error rate (BER) of different multichannel transmission systems compared with one another, against the optical signal-to-noise ratio (OSNR) while taking into account the intersymbol interference (ISI).

Claims

1. Coding method for multichannel optical transmission systems, in which coding is carried out both in the time direction and over a plurality of channels, wherein a mapping is selected for the coding such that the simultaneous occurrence of bits with a signal value of ‘1’ in neighbouring channels is excluded.

2. Coding method according to claim 1, wherein a code design with a maximal Hamming distance is selected.

3. Coding method according to claim 1o, wherein a code design with minimal Hamming weights is selected.

4. Coding method according to claim 1, wherein a code design with a minimal number of ‘0 1’ and ‘1 0’ bit patterns in the time direction is selected.

5. Coding method according to claim 1, wherein all possible codewords are evaluated in the decoding, and the codeword with the maximal metric is selected.

6. Coding method according to claim 1, wherein the least likely codewords are excluded by means of an algorithm before the actual decoding.

7. Coding method according to claim 1, wherein the channels are grouped in pairs, the coding being carried out over the channels grouped in pairs.

8. Coding method according to claim 1, wherein the channels are grouped in triples, the coding being carried out over the channels grouped in triples.

9. Coding method according to claim 1, wherein the interchannel-time coding is combined with Reed-Solomon coding.

10. Multichannel optical transmission system for carrying out the coding method according to claim 1, comprising means arranged on the transmitter side for the interchannel-time coding of a plurality of channels which can be transmitted by means of an optical fibre link and means arranged on the receiver side for decoding the channels transmitted via the optical fibre link, the interchannel-time coding means comprising means for carrying out a mapping such that the simultaneous occurrence of bits with a signal value of ‘1’ in neighbouring channels is excluded.

11. Multichannel optical transmission system according to claim 10, wherein a maximum likelihood symbol-by-symbol decoder is used for the decoding.

12. Multichannel optical transmission system according to claim 10, wherein a sphere decoder is used for the decoding.

13. Multichannel optical transmission system according to claim 10, comprising means for additionally carrying out Reed-Solomon coding.

14. Coder comprising means for the interchannel-time coding of transmission sequences of neighbouring channels, wherein the means for the interchannel-time coding of neighbouring channels comprise means for carrying out a mapping such that the simultaneous occurrence of bits with a signal value of ‘1’ in neighbouring channels is excluded.